Centralizer for wireline tool

Abstract

A centralizer assembly replaces an existing centralizer of a wireline tool so the tool can be used with smaller casing, such as casing smaller than 6-in. The assembly includes first and second centralizer units that replace the existing centralizer on a mandrel. Each unit has a sleeve that fits in a recess of the mandrel, and each unit has slider blocks disposed together in the recess on opposing sides of a divider on the sleeve. Arms hingedly connected to the blocks on each unit connect together at a joint having a roller for engaging in the casing. On each unit, a common pin is disposed through the slider blocks, and biasing elements on the common pin bias the blocks toward one another with different amounts of bias.

What is claimed is: 
     
       1. An assembly for converting a given centralizer of a wireline tool for use with smaller diameter casing, the wireline tool having a mandrel with first and second recesses separated by an upset, the given centralizer having first and second slider blocks disposed respectively in the first and second recesses and having a plurality of given radial supports, each of the given radial supports having a first arm hingedly connected to the first slider block, each of the radial supports having a second arm hingedly connected to the second slider block and hingedly connected to the first arm, the assembly comprising:
 first and second centralizers replacing the given centralizer on the mandrel, 
 the first centralizer having a first divider disposed in the first recess and having third and fourth slider blocks disposed together in the first recess on respective sides of the first divider, the first centralizer having a third arm hingedly connected to the third slider block, the first centralizer having a fourth arm hingedly connected to the fourth slider block and hingedly connected to the third arm; and 
 the second centralizer having a second divider disposed in the second recess and having fifth and sixth slider blocks disposed together in the second recess on respective sides of the second divider, the second centralizer having a fifth arm hingedly connected to the fifth slider block, the second centralizer having a sixth arm hingedly connected to the sixth slider block and hingedly connected to the fifth arm. 
 
     
     
       2. The assembly of  claim 1 , wherein each of the respective slider blocks comprises at least two pieces fitting together in the respective recess around the mandrel. 
     
     
       3. The assembly of  claim 1 , wherein each of the first and second dividers comprises a sleeve disposed in the respective recess, the sleeve having a shoulder for the respective divider and having the respective slider blocks disposed on the sleeve on opposing sides of the shoulder. 
     
     
       4. The assembly of  claim 3 , wherein each of the sleeves comprises at least two pieces fitting together in the respective recess around the mandrel. 
     
     
       5. The assembly of  claim 1 , wherein each of the respective slider blocks for the first and second centralizers comprises a common pin disposed through adjacent shoulders on the respective slider blocks, the common pin having a first shoulder end and having a first biasing element disposed on the common pin between the first shoulder end and a first of the adjacent shoulders, the common pin having a second shoulder end and having a second biasing element disposed on the common pin between the second shoulder end and a second of the adjacent shoulders. 
     
     
       6. The assembly of  claim 5 , wherein the first biasing element comprises a first stiffnesses; and wherein the second biasing element comprises a second stiffness different from the first stiffness. 
     
     
       7. The assembly of  claim 5 , wherein a first shouldering distance between the first end of the common pin and the first adjacent shoulder is greater than a second shouldering distance between the second end of the common pin and the second adjacent shoulder. 
     
     
       8. The assembly of  claim 1 , wherein the first centralizer comprises a plurality of first radial supports, each of the first radial supports having a set of the third and fourth arms; and wherein the second centralizer comprises a plurality of second radial supports, each of the second radial supports having a set of the fifth and sixth arms. 
     
     
       9. The assembly of  claim 8 , wherein the first radial supports are arranged about the third and fourth slider blocks alternatingly closer to edges of the third and fourth slider blocks. 
     
     
       10. A centralizer for use on a wireline tool in casing having a number of inner diameters, the wireline tool having a mandrel with a dividing upset, the centralizer comprising:
 a first slider block disposed on the mandrel on a first side of the dividing upset; 
 a second slider block disposed on the mandrel on a second side of the dividing upset, the first and second slider blocks being separable from one another; 
 a first arm hingedly connected to the first slider block; 
 a second arm hingedly connected to the second slider block and hingedly connected to the first arm; 
 a common pin disposed between the first and second slider blocks; 
 a first biasing element arranged between the common pin and at least one of the first and second slider blocks; and 
 a second biasing element arranged between the common pin and at least one of the first and second slider blocks, the first biasing element being configured to bias the common pin and the at least one of the first and second slider blocks for an initial extent of separation between the first and second slider bocks, the second biasing element being configured to bias the common pin and the at least one of the first and second slider blocks for a subsequent extent of the separation between the first and second slider bocks. 
 
     
     
       11. The centralizer of  claim 10 ,
 wherein the first slider block comprises a first shoulder facing away from the dividing upset; 
 wherein the second slider block comprises a second shoulder facing away from the dividing upset; 
 wherein the common pin is disposed through the first and second shoulders on the respective slider blocks, the common pin having third and fourth shoulders; 
 wherein the first biasing element is disposed on the common pin between the first shoulder of the first slider block and the third shoulder of the common pin; and 
 wherein the second biasing element is disposed on the common pin between the second shoulder of the second slider block and the fourth shoulder end of the common pin. 
 
     
     
       12. The centralizer of  claim 11 , wherein the first biasing element comprises a first stiffnesses; and wherein the second biasing element comprises a second stiffness different from the first stiffness. 
     
     
       13. The centralizer of  claim 11 , wherein a first shouldering distance between the first shoulder of the first slider block and the third shoulder of the common pin is greater than a second shouldering distance between the second shoulder of the second slider block and the fourth shoulder of the common pin. 
     
     
       14. The centralizer of  claim 10 , wherein the first biasing element comprises a first stiffnesses, and the second biasing element comprises a second stiffness different from the first stiffness; and/or wherein the initial extent is shorter than the subsequent extent. 
     
     
       15. The centralizer of  claim 10 , wherein the centralizer comprises a plurality of first radial supports, each of the radial supports having a set of the first and second arms. 
     
     
       16. The centralizer of  claim 10 ,
 wherein the first slider block comprises a first shoulder facing away from the dividing upset; 
 wherein the common pin is connected from the second slider block and is disposed through the first shoulder on the first slider block, the common pin having a second shoulder; 
 wherein the first biasing element is disposed on the common pin between the first shoulder of the first slider block and the second biasing element; and 
 wherein the second biasing element is disposed on the common pin between the second shoulder of the common pin and the first biasing element. 
 
     
     
       17. A centralizer for use on a wireline tool in casing having a number of inner diameters, the wireline tool having a mandrel, the centralizer comprising:
 a sleeve disposed on the mandrel, the sleeve having a dividing upset; 
 a first slider block disposed on the sleeve on a first side of the dividing upset; 
 a second slider block disposed on the sleeve on a second side of the dividing upset, the first and second slider blocks being separable from one another; 
 a first arm hingedly connected to the first slider block; 
 a second arm hingedly connected to the second slider block and hingedly connected to the first arm; 
 a first biasing element arranged between the first and second slider blocks; and 
 a second biasing element arranged between the first and second slider blocks, the first biasing element biasing an initial extent of separation between the first and second slider bocks, the second biasing element biasing a subsequent extent of the separation between the first and second slider bocks. 
 
     
     
       18. The centralizer of  claim 17 ,
 wherein the first slider block comprises a first shoulder facing away from the dividing upset; 
 wherein the second slider block comprises a second shoulder facing away from the dividing upset; 
 wherein the centralizer comprises a common pin disposed through the first and second shoulders on the respective slider blocks, the common pin having third and fourth shoulders; 
 wherein the first biasing element is disposed on the common pin between the first shoulder of the first slider block and the third shoulder of the common pin; and 
 wherein the second biasing element is disposed on the common pin between the second shoulder of the second slider block and the fourth shoulder end of the common pin. 
 
     
     
       19. The centralizer of  claim 18 , wherein a first shouldering distance between the first shoulder of the first slider block and the third shoulder of the common pin is greater than a second shouldering distance between the second shoulder of the second slider block and the fourth shoulder of the common pin. 
     
     
       20. The centralizer of  claim 17 , wherein the first biasing element comprises a first stiffnesses, and the second biasing element comprises a second stiffness different from the first stiffness; and/or wherein the initial extent is shorter than the subsequent extent. 
     
     
       21. The centralizer of  claim 17 , wherein the centralizer comprises a plurality of first radial supports, each of the radial supports having a set of the first and second arms. 
     
     
       22. The centralizer of  claim 17 ,
 wherein the first slider block comprises a first shoulder facing away from the dividing upset; 
 wherein the centralizer comprises a common pin connected from the second slider block and disposed through the first shoulder on the first slider block, the common pin having a second shoulder; 
 wherein the first biasing element is disposed on the common pin between the first shoulder of the first slider block and the second biasing element; and 
 wherein the second biasing element is disposed on the common pin between the second shoulder of the common pin and the first biasing element.